1. Field of the Invention
This invention relates to novel 4-benzazonine derivatives and their salts having therapeutical activities on the central nervous system with low toxicity, and to processes for the preparation of these derivatives and salts.
2. Description of the Prior Art
It is known that 3-benzazonine derivatives which are considered to be compounds having a morphinan structure in which the ring C is cleft have an analgesic activity. Among these derivatives, 1, 2, 3, 4, 5, 6-hexahydro-3-(3-methyl-2-butenyl)-6, 11-dimethyl-8-hydroxy-2, 6-methano-3-benzazonine generally called "pentazocine"; Journal of Medicinal Chemistry, 7, 123 (1964) and Chemical Abstracts, 58, 2440.sup.b (1963) is used for therapeutic purposes. Morphinan and pentazocine have structures represented by the following formulae: ##STR3##